Final answer:
Meiosis in an organism with a 2n number of 80 will result in cells with 40 chromosomes (n=40), and these cells are gametes. Fertilization restores the diploid number but does not create pairs of chromosomes, and mitosis maintains the 80 chromosome count in daughter cells. Therefore, option b) is the correct statement.
Step-by-step explanation:
Understanding the Chromosome Number During Meiosis and Fertilization
In the life cycle of an animal with a diploid number (2n) of 80 chromosomes, several events related to cell division occur. When meiosis takes place, it will result in the production of cells that have half the number of chromosomes from the parent cell. Since the organism has a diploid number of 80, meiosis will result in cells with 40 chromosomes (n=40), these cells being gametes such as sperm or eggs. The statement b) is correct.
Upon fertilization, when two of these haploid gametes (each with 40 chromosomes) fuse, they will create a zygote with a diploid number of chromosomes, that is, 80 chromosomes in total, but not in pairs. Thus, option c) is incorrect since the zygote will not have 80 pairs but rather 80 individual chromosomes from the two sets of 40 that were combined.
Following the formation of the zygote, as the new organism develops, mitosis will produce cells that are genetically identical to the parent cell, maintaining the diploid chromosome number. Therefore, mitotic division will result in cells with 80 chromosomes, making option d) incorrect.
Lastly, option e) is not correct because gametes, which are products of meiosis, contain only individual chromosomes, not pairs, so they won't have 40 homologous pairs.